A library used to position poppers in web applications.

A popper is an element on the screen which "pops out" from the natural flow of your application.
Common examples of poppers are tooltips, popovers, and drop-downs.

Well, basically, no.
Popper.js is a positioning engine; its purpose is to calculate the position of an element to make it possible to position it near a given reference element.

The engine is completely modular, and most of its features are implemented as modifiers (similar to middlewares or plugins).
The whole code base is written in ES2015, and its features are automatically tested on real browsers thanks to SauceLabs and TravisCI.

Popper.js has zero dependencies. No jQuery, no LoDash, nothing.
It's used by big companies like Twitter in Bootstrap v4, Microsoft in WebClipper, and Atlassian in AtlasKit.

This is the engine, the library that computes and, optionally, applies the styles to the poppers.

Some of the key points are:

• Position elements keeping them in their original DOM context (doesn't mess with your DOM!);
• Allows to export the computed information to integrate with React and other view libraries;
• Supports Shadow DOM elements;
• Completely customizable thanks to the modifiers based structure;

Visit our project page to see a lot of examples of what you can do with Popper.js!

Find the documentation here.

Since lots of users just need a simple way to integrate powerful tooltips in their projects, we created Tooltip.js.
It's a small library that makes it easy to automatically create tooltips using as engine Popper.js.
Its API is almost identical to the famous tooltip system of Bootstrap, in this way it will be easy to integrate it into your projects.
The tooltips generated by Tooltip.js are accessible thanks to the aria tags.

Find the documentation here.

Popper.js is available on the following package managers and CDNs:

Tooltip.js as well:

*: Bower isn't officially supported, it can be used to install Tooltip.js only through the unpkg.com CDN. This method has the limitation of not being able to define a specific version of the library. Bower and Popper.js suggest using npm or Yarn for your projects.
For more info, read the related issue.

Popper.js is currently shipped with 3 targets in mind: UMD, ESM, and ESNext.
No idea what am I talking about? You are looking for UMD probably.

• UMD - Universal Module Definition: AMD, RequireJS, and globals;
• ESM - ES Modules: For webpack/Rollup or browser supporting the spec;
• ESNext: Available in /dist, can be used with webpack and babel-preset-env;

Make sure to use the right one for your needs. If you want to import it with a <script> tag, use UMD.
If you can't find the /dist folder in the Git repository, this is because the distribution files are shipped only to Bower, npm or our CDNs. You can still find them visiting https://unpkg.com/popper.js/dist/ (or https://unpkg.com/tooltip.js/dist/)

Given an existing popper DOM node, ask Popper.js to position it near its button.

var reference = document.querySelector('.my-button');
var popper = document.querySelector('.my-popper');
var anotherPopper = new Popper(reference, popper, {
  // popper options here
});

Popper.js supports two kinds of callbacks; the onCreate callback is called after the popper has been initialized. The onUpdate one is called on any subsequent update.

const reference = document.querySelector('.my-button');
const popper = document.querySelector('.my-popper');
new Popper(reference, popper, {
  onCreate: data => {
    // data is an object containing all the informations computed
    // by Popper.js and used to style the popper and its arrow
    // The complete description is available in Popper.js documentation
  },
  onUpdate: data => {
    // same as `onCreate` but called on subsequent updates
  },
});

Popper.js is based on a "plugin-like" architecture, most of its features are fully encapsulated "modifiers".
A modifier is a function that is called each time Popper.js needs to compute the position of the popper. For this reason, modifiers should be very performant to avoid bottlenecks.

To learn how to create a modifier, read the modifiers documentation

Integrating 3rd party libraries to React or other libraries can be a pain because they usually alter the DOM and drive the libraries crazy.
Popper.js limits all its DOM modifications inside the applyStyle modifier, you can simply disable it and manually apply the popper coordinates using your library of choice.

For a comprehensive list of libraries that let you use Popper.js into existing frameworks, visit the MENTIONS page.

Alternatively, you may even override your own applyStyles with your custom one and integrate Popper.js by yourself!

function applyReactStyle(data) {
  // export data in your framework and use its content to apply the style to your popper
}

const reference = document.querySelector('.my-button');
const popper = document.querySelector('.my-popper');
new Popper(reference, popper, {
  modifiers: {
    applyStyle: { enabled: false },
    applyReactStyle: {
      enabled: true,
      fn: applyReactStyle,
      order: 900,
    },
  },
});

It is recommended that users mock Popper.js for use in Jest tests due to some limitations of JSDOM.

The simplest way to mock Popper.js is to place the following code in __mocks__/popper.js.js adjacent to your node_modules directory. Jest will pick it up automatically.

import PopperJs from 'popper.js';

export default class Popper {
  static placements = PopperJs.placements;

  constructor() {
    return {
      destroy: () => {},
      scheduleUpdate: () => {},
    };
  }
}

Alternatively, you can manually mock Popper.js for a particular test.

jest.mock('popper.js', () => {
  const PopperJS = jest.requireActual('popper.js');

  return class Popper {
    static placements = PopperJS.placements;

    constructor() {
      return {
        destroy: () => {},
        scheduleUpdate: () => {},
      };
    }
  };
});

Since the API changed, we prepared some migration instructions to make it easy to upgrade to Popper.js v1.

floating-ui#62

Feel free to comment inside the issue if you have any questions.

Popper.js is very performant. It usually takes 0.5ms to compute a popper's position (on an iMac with 3.5G GHz Intel Core i5).
This means that it will not cause any jank, leading to the smooth user experience.

The aim of Popper.js is to provide a stable and powerful positioning engine ready to be used in 3rd party libraries.

Visit the MENTIONS page for an updated list of projects.

I want to thank some friends and projects for the work they did:

• @AndreaScn for his work on the GitHub Page and the manual testing he did during the development;
• @vampolo for the original idea and for the name of the library;
• Sysdig for all the awesome things I learned during these years that made it possible for me to write this library;
• Tether.js for having inspired me in writing a positioning library ready for the real world;
• The Contributors for their much appreciated Pull Requests and bug reports;
• you for the star you'll give to this project and for being so awesome to give this project a try 🙂

Code and documentation copyright 2016 Federico Zivolo. Code released under the MIT license. Docs released under Creative Commons.